This study aims to quantify the solar wind charge-exchange (SWCX) X-ray emission factor (denoted as α-value) and its dependence on solar wind parameters, solar activity cycle, and solar wind origin. By analyzing 13-year (1998–2011) in-situ measurements from the advanced composition explorer (ACE) spacecraft, we investigate the statistical correlations between solar wind ionization states, elemental abundances (particularly oxygen), and bulk plasma parameters (proton speed, density). The derived α-values are critical for explaining the data from solar wind and magnetosphere interaction linker explorer (SMILE), and disentangling SWCX foreground emissions from diffuse astrophysical X-ray sources observed by Einstein Probe (EP) and proposed diffuse X-ray explorer (DIXE) payload on Chinese space station. In this work, high-resolution solar wind ion composition data and plasma parameters from ACE are investigated. Events are categorized by solar wind origin (coronal holes, streamers, interplanetary coronal mass ejections (ICMEs)) and solar cycle phase (minimum vs. maximum). The α-value, defined as the total soft X-ray photon emission cross section per solar wind proton, is computed using an updated charge-exchange model that combines the state-resolved cross-section for highly charged ions. The model takes into consideration the velocity-dependent cross-section of solar wind-neutral interaction. Statistical method and bin-averaging techniques are adopted to extract the relations between α, solar wind speed (v_sw), proton density (n_p), and oxygen abundance. The main results are as follows.

1) Ionization state dynamics: A strong anti-correlation exists between solar wind ionization degree and bulk speed: high-speed winds (> 500 km/s) exhibit lower ionization states than slow-speed winds (< 400 km/s).

2) Elemental abundance trends: Oxygen abundance (O/H) is inversely correlated with n_p: the O/H of denser solar wind plasmas (n_p > 13 cm^–3) decreases by 30%–50%, indicating the presence of fractionation during plasma acceleration. No significant speed dependence of O/H is observed, compared with earlier research results.

3) Emission factor (α-value) behavior: α-value decreases rapidly with the increase of n_p and stabilizes for n_p > 13 cm⁻³. Conversely, α-value increases gradually with v_sw up to 430 km/s, beyond which it plateaus. The ICME-associated α exceeds streamer and coronal hole values by 35%–60%, which is attributed to higher averaged ionic state in transient ejecta. Solar maximum α (2000–2002) is 1.3–2.7 times higher than solar minimum (2008–2010), reflecting cycle-dependent ion composition changes.

By bridging in-situ solar wind measurements and X-ray emission physics, this work enhances the ability to diagnose solar wind-magnetosphere coupling and diffuse X-ray background. The validated α-value will be of benefit to the data analysis for Chinese aerospace projects in the 2020s, such as SMILE, DIXE, and EP.